1. Field of the Invention
The present invention relates to a vertically-stacked plate interdigital capacitor structure, and more particularly, to a vertically-stacked plate interdigital capacitor structure having a plurality of rectangular metal vias.
2. Description of the Prior Art
Various capacitor structures are used as electronic elements in integrated circuits such as radio frequency integrated circuits (RFIC), and monolithic microwave integrated circuits (MMIC). Such capacitor structures include, for example, metal-oxide-semiconductor (MOS) capacitors, p-n junction capacitors and metal-insulator-metal (MIM) capacitors. For some applications, MIM capacitors can provide certain advantages over MOS and p-n junction capacitors because the frequency characteristics of MOS and p-n junction capacitors may be restricted as a result of depletion layers that form in the semiconductor electrodes. An MIM capacitor can exhibit improved frequency and temperature characteristics. Furthermore, MIM capacitors are formed in the metal interconnect layers, thereby reducing transistor process integration interactions or complications.
Please refer to FIG. 1, which is a schematic diagram of a conventional MIM capacitor structure 10. As shown in FIG. 1, the conventional MIM capacitor structure 10 includes a lower metal plate 12, an upper metal plate 14 positioned over the lower metal plate 12, and an inter-metal dielectric layer 16 disposed in between the lower metal plate 12 and the upper metal plate 14. Since the capacitance of the MIM capacitor structure 10 is directly proportional to the area of the lower metal plate 12 and the upper metal plate 14, the area of the MIM capacitor structure 10 must be maintained in a large scale so as to increase the capacitance. As shown in FIG. 1, the lower metal plate 12 and the upper metal plate 14 are overlapped, and the horizontal planar area between the lower metal plate 12 and the upper metal plate 14 is very large. However, due to the requirements of electronic device miniaturization, the size of the MIM capacitor structure 10 becomes a problem in diminishing the overall size of the electronic devices. Therefore, a new capacitor structure, which has a smaller size but possesses a large capacitance, is beneficial for the fabrication of miniature electronic devices.